Pattern matching in quanteda using the valuetype argument.
the type of pattern matching: "glob" for "glob"-style
wildcard expressions; "regex" for regular expressions; or "fixed" for
exact matching. See valuetype for details.
logical; if TRUE, ignore case when matching a
pattern or dictionary values
Pattern matching in in quanteda uses "glob"-style pattern
matching as the default, because this is simpler than regular expression
matching while addressing most users' needs. It is also has the advantage
of being identical to fixed pattern matching when the wildcard characters
(* and ?) are not used. Finally, most dictionary formats use glob
matching.
"glob""glob"-style wildcard expressions, the quanteda
default. The implementation used in quanteda uses * to match any
number of any characters including none, and ? to match any single
character. See also utils::glob2rx() and References below.
"regex"Regular expression matching.
"fixed"Fixed (literal) pattern matching.
If "fixed" is used with case_insensitive = TRUE, features will
typically be lowercased internally prior to matching. Also, glob matches
are converted to regular expressions (using utils::glob2rx()) when
they contain wild card characters, and to fixed pattern matches when they
do not.